js发布订阅模式

export var msgHandler = {};

/**
 * 消息队列
 */
msgHandler.msgQueue = {};

/**
 * 订阅消息
 * @param {消息类型} eventType 
 * @param {回调方法} handler 
 */
msgHandler.on = (eventType, handler) => {
    if (!(eventType in msgHandler.msgQueue)) {
        msgHandler.msgQueue[eventType] = [];
    }

    msgHandler.msgQueue[eventType].push(handler);
}

/**
 * 订阅
 * @param {消息类型}} eventType 
 * @param {数据} data 
 */
msgHandler.emit = (eventType, data) => {
    for (var i = 0; msgHandler.msgQueue[eventType] && i < msgHandler.msgQueue[eventType].length; i++) {
        msgHandler.msgQueue[eventType][i].call(this, data);
    }
}

/**
 * 
 * @param {消息类型}} eventType 
 * @param {回调方法} handler 
 */
msgHandler.off = (eventType, handler) => {
    var currentEvent = msgHandler.msgQueue[eventType];
    var len = 0;
    if (currentEvent) {
        len = currentEvent.length;
        for (var i = len - 1; i >= 0; i--) {
            if (currentEvent[i] === handler) {
                currentEvent.splice(i, 1);
            }
        }
    }
}